FIG. 1 illustrates the general wireless packet flow infrastructure 100 between wireless devices 102, 104 and the Internet 116. Clients 102,104 connect to an Access Point (AP) 106 wherein data will be transmitted through an IP CAPWAP (Wireless Access Points protocol) tunnel 108 to a wireless controller (WLC) 110. Packets will then be natively layer 2 (L2) forwarded 112, 113 to/from Internet gateway (GW) router 114 for connecting to the Internet 116.
A WLC 110 can handle hundreds of thousands of wireless clients 102/104. The WLC 110 needs to be highly redundant with high availability. When the active WLC 110 goes down, a standby WLC 118 takes over. The wireless clients 102/104 and the AP 106 states are synced over from the active WLC 110 to the standby WLC 118. The AP 106 also needs to switch to the new active WLC 118 with a new CAPWAP tunnel end-point 120. After the WLC fail-over, the clients 102/104 to/from the WLC portion of the traffic is handled in a fast convergence fashion such that within one second, for example, the traffic from the clients 102/104 is communicated from the AP 106 through the new tunnel 120 to the new WLC 118. The AP 106 can represent multiple devices and even hundreds to thousands of devices.
However, there are additional challenges in the failover process. The portion of the network between the WLC 110 and the GW 114 is a L2 switch or switch domain 112, 113. For traffic from the GW 114 to the WLC 110, the MAC (Media Access Control) learning had the path from the GW 114 to the former active WLC device 110. The L2 switch network 112 will not know that the new active WLC 118 has taken over all the client MAC addresses. The challenge in the fail-over scenario is that it takes real traffic for each of the MAC addresses of the clients 102/104 to be relearned in order for GW 114 to reach the new active WLC device 118.
One way to handle relearning all of the MAC addresses after a fail-over to the new active WLC 118. The new active WLC 118 will send out gratuitous ARP (Address Resolution Protocol) signals for each of the clients 102/104 to advertise that the new WLC 118 now owns those MAC addresses. But to handle hundreds of thousands of wireless client MAC devices, at the moment right after switchover and the device is very busy, would take a while for all MAC addresses to be finally relearned in the L2 domain 113.
Thus, even if the system implements an efficient and speedy synchronization of the clients' information from the active WLC 110 to the standby WLC 118, if the system does not implement a scalable solution to deal with the re-convergence of hundreds of thousands of wireless clients on the L2 domain, there remains a need within the art for a faster convergence approach.